Turbine

ABSTRACT

A turbine for a compressible medium in which one or more regulating valves directly communicate(s) with the distribution duct(s) around the wheel of a centripetal stage, regulating valves first converging gradually and then gradually diverging a valve body extending into the diverging part of the housing by a portion whose sectional area gradually decreases in accordance with a linear function of the place of said section on the longitudinal axis of the valve body, in the closed state the valve body being in contact on the upstream side of the converging part with the housing along a common tangential plane which is at an angle to the direction of movement of the valve body, which angle exceeds the friction angle between the valve body and the housing.

United States Patent Schrieken TURBINE Inventor: Jan Schrieken, Delden,Netherlands Koninklijke Machinefabriek Stork B.V., Hengelo, NetherlandsSept. 12, 1973 Assignee:

Filed:

Appl. No.:

References Cited UNITED STATES PATENTS 1451 May 13, 1975 PrimaryExaminer-Henry F. Raduazo Attorney, Agent, or Firm-Snyder, Brown andRamik [5 7] ABSTRACT into the diverging part of the housing by a portionwhose sectional area gradually decreases in accordance with a linearfunction of the place of said sec tion on the longitudinal axis of thevalve body, in the closed state the valve body being in contact on theupstream side of the converging part with the housing along a commontangential plane which is at an angle 1,412,257 4/1922 Petsche 415/15129 4 7 950 Ange" 1 4 5 205 to the d1rect1on of movement of the valvebody, whlch 3,479,124 11/1969 Hendriks 1. 415/159 angle exceeds thefriction angle between the valve FOREIGN PATENTS 0R APPLICATIONS andhousmg' 474,916 7/1951 Canada ,1 415/151 9 Claims, 4 Drawing Figures 3 L1 l2 1 n 9 8 l0 TURBINE The invention relates to a turbine for acompressible medium comprising one or more wheels, among which at leastthe wheel of the first stage is traversed in the centripetal directionby the driving medium and operates in accordance with the equal-pressureprinciple, said stage being surrounded by one or more distribution ductsarranged around the centripetal wheel, in which one or more regulatingvalves in which an enthalpy difference of the medium is converted intovelocity, is (are) directly connected by the outlet opening with theinlet side of the distribution duct (s) and, viewed from the inlet end,the distribution duct (s) exhibit(s) a gradually decreasing flow passageand directly join(s) along the whole inner circumference the centripetalwheel, said regulating valves being formed by a housing provided with avalve body, the passage of which first converges and subsequentlydiverges. The invention has for its object to provide such a turbine inwhich the regulating valve in which the velocity of the compressiblemedium is produced has a particularly advantageous structure. Accordingto the invention the regulating valve is formed by a valve housing whosepassage in the direction of flow first converges gradually and thengradually diverges, there being provided a valve body which leaves freea narrow gap at the area of the smallest diameter of the housing in theclosed state and extends into the diverging part of the housing by aportion whose sectional area gradually decreases according to a linearfunction of the place of said sectional area on the longitudinal axis ofthe valve body, whilst in the closed state of the valve body it is incontact on the upstream side of the converging part, with the housingalong a common tangential plane which is at an angle to the direction ofmovement of the valve body, which angle exceeds the friction anglebetween the valve body and the housing.

Thus a valve housing is obtained which comprises a portion whose passagegradually converges, in which the flow is subsonically accelerated, anarrowest place, the neck, where the velocity of sound is attained and aportion whose passage gradually diverges, in which the flow issupersonically accelerated after the valve with a sufficiently lowpressure. It should be noted that in the turbine according to theinvention one is not concerned with an optimum restoration of pressure,but it is intended to produce an optimally matching high velocity.

Since beyond the narrowest part of the passage of the housing the valvebody extends in the diverging portion, the divergence of the availablepassage of the pressurized medium continues varying gradually in allstates of partial load. Owing to the linear variation of the surface ofthe sectional area of the valve body the quantity of medium allowed topass through the valve varies linearly with the stroke of the valvebody. Since closure of the passage with the aid of the valve body doesnot take place at the narrowest section of the passage, it can beavoided that the valve body becomes jammed in the housing. Since theclosing area is located in a considerably larger section than that ofthe smallest passage of the housing, the gap at the area of thenarrowest passage of the housing will exhibit the smallest passagealready at a very slight displacement of the valve body and will becomedeterminative for the quantity of passing medium. Consequently, thelinear control occurs not until the valve has performed a small stroke.At the area of closure the shape of the valve body and of the housing isvery disadvantageous from the view-point of flow technology. However,owing to the large section in which the closure is made thisdisadvantage is negligible because in this area the velocity remainsvery low as compared with that in the narrowest section.

The invention will now be described more fully with reference to anembodiment of a regulating valve. In the drawing FIG. 1 is a schematiccross sectional view of a turbine embodying the invention.

FIG. 2 is a schematic sectional view of a valve body with theco-operating portion of the housing in the closed state,

FIG. 3 shows the valve body of FIG. 2 in the semiopened state and FIG. 4shows the valve body of FIG. 2 in the completely opened state.

The turbine shown in FIG. 1 comprises a housing 1 in which thecentripetal stage is arranged. The wheel 2 of the centripetal stage isarranged in a housing 3, which is suspended in the housing 1. Thehousing 3 comprises distribution ducts 4 and 5, with which communicateregulating valves 6 and 7 respectively. As is shown in detail for theregulating valve 6, it comprises a housing 8 fastened to the housing Iby flanges 9. The housing 8 accomodates a guide 10 for guiding a valvestem 11 holding a valve body 12. The valve body 12 is adapted toco-operate with an exchangeable part 13, which is secured in the housing8. The exchangeable part 13 joins the housing 3 through a gap 14. It isthus avoided that in the event of temperature differences between thecomponents high stresses would be produced. FIGS. 2, 3 and 4 show thevalve body 12 on an enlarged scale, whilst in addition the portion ofthe exchangeable part 13 co-operating with the valve body 12 is shown.

The shape of the part 13 is such that, as is shown in FIG. 4, first aconverging portion 15, in which the flow can be subsonically acceleratedand then a narrowest place at 16, where the velocity of sound isattained and then a portion 17, in which the passage gradually diverges.With a sufficiently low pressure after the valve body 12 the flow isfurther accelerated supersonically. Between I8 and 19 the valve body I2exhibits a variation in section which is linear with respect to thelongitudinal axis of the body. As a result the narrowest passage betweenthe valve body 12 and the part 13 and hence the passed quantity ofmedium will vary linearly with the stroke. This is desirable for thetechnical control.

At 20 the valve body 12 has a thickened part. In the closed state of thevalve body shown in FIG. 2 this thickened part is in contact with thewall of the part I3 ofthe housing. In the closed state the thickenedpart 20 is in contact at 21 with the part 13. The closing area 20, 21 islocated upstream from the narrowest part 16 in a much larger sectionalarea than that of the part 16. This results in that at the movement ofthe valve body 12 out of the position shown in FIG. 2 the narrowestpassage is initially located at 20 and 21, but fairly immediately thenarrowest passage will be located at 16. Thus the linear controlcharacteristic occurs as soon as the valve body has performed a veryslight stroke. In FIG. 2 the angle between the contact planes at 20 and21 and the direction of movement, when the valve body is in the closedstate, is designated by a. The angle a to the direction of movement ofthe valve body exceeds the friction angle between the valve body 12 andhousing part 13. Thus in operation the valve body will never be jammeddue to self-braking.

The technically disadvantageous shape of the part 13 at 21 and of thevalve body at is unobjectionable since in the opened states illustratedin FIGS. 3 and 4 these parts are located in a zone where only low velocity prevails owing to the large passage. When the turbine is locatedonly partially, the drop in pressure across the centripetal stage willincrease. This means that in order to maintain a low degree of reactionalso the drop in pressure across the regulating valve has to increase.For this purpose a larger divergence of the passage available isrequired beyond the narrowest passage at 16. The passage of the portion17 is constant and since with partial load the portion located between18 and 19 co-operates with the portion 17, a larger divergence is,indeed, obtained beyond the narrowest passage in the position shown inFIG. 3 than in the case of full load, when the valve body is in theposition shown in FIG. 4. Since in all partial load positions the partof the valve body located between 18 and 19 extends as far as into theportion 17 a gradual variation of the divergence is obtained in allpositions.

What we claim is:

l. A turbine for a compressible medium having at least a first stagewheel which is traversed in the centripetal direction by the drivingmedium and operates in accordance with the equal pressure principle,said stage being at least partially surrounded by a distribution duct ofdecreasing cross section, a regulating valve controlling flow into saiddistribution duct and at which an enthalpy difference of the medium isconverted into velocity, said valve comprising a housing provided with avalve body and having a passage which first converges and then divergesand characterised in that in the direction of flow the passage of thevalve housing first converges abruptly and then gradually diverges andin that the valve body leaves free, in the closed state, a narrow gap atthe area of the smallest section of the housing and extends into thediverging part of the housing by a portion whose sectional areagradually decreases in accordance with a linear function of the place ofsaid sec tion on the longitudinal axis of the valve body and in that inthe closed state the valve body is in contact on the upstream side ofthe converging part with the housing along a common tangential planewhich is at an angle to the direction of movement of the valve body,which angle exceeds the friction angle between the valve body and thehousing.

2. In a turbine driven by a compressible fluid and including at leastone turbine wheel having radial vanes, a housing surrounding saidturbine wheel and defining at least one distribution duct having aninlet end and extending from said inlet end circumferentially of saidturbine wheel in progressively decreasing cross section, the improvementwhich comprises a body portion defining a valve-controlled dischargepassage which discharges the compressible fluid axially into said inletend of the distribution duct;

said discharge passage being defined by the inner surface of said bodyportion and having a constriction spaced from said inlet end of thedistribution duct, a divergent portion leading from said constriction tosaid inlet opening, and a convergent portion leading to saidconstriction;

a valve member concentrically disposed and axially movable within saiddischarge passage, said valve member including a head having a shoulderportion presenting a downstream face engagable with essentially onlyline contact with said convergent portion of the discharge passageupstream of said constriction when the valve is closed, and a rounded,generally conical nose having its base merging with said downstream faceand presenting throughout a cross section smaller than that of saidconstriction, said convergent portion of the discharge passage leadingabruptly into said constriction to provide an annular clearance areaaround said shoulder portion of the valve member, when same is closed,which is substantially larger than the annular clearance between saidnose and said constriction whereby the angle of engagement between saidvalve member and said body portion along said line contact is greaterthan the friction angle between such members and wherein the clearancebetween the nose and the constriction establishes flow controlsubstantially as soon as said line contact between said downstream faceof the valve member and said convergent portion of the discharge passageis broken; and

means for axially shifting said valve member between said closedposition and a fully open position in which the tip of said nose of thevalve member remains within said constriction.

3. In a turbine as defined in claim 2 wherein said nose is contoured toestablish a substantially linear relation between axial shifting of saidvalve member and the change of cross sectional clearance area betweenthe nose and constriction effected by such shifting throughout the rangeof movement of said valve member.

4. In a turbine as defined in claim 3 wherein said downstream face ofthe valve member is concave.

5. In a turbine as defined in claim 4 wherein that portion of saidconvergent portion of the discharge passage upstream of and immediatelyadjacent line contact is concave whereas that portion thereof downstreamof and leading to said constriction is convex.

6. In a turbine as defined in claim 2 wherein said downstream face ofthe valve member is concave.

7. In a turbine as defined in claim 6 wherein that portion of saidconvergent portion of the discharge passage upstream of and immediatelyadjacent line contact is concave whereas that portion thereof downstreamof and leading to said constriction is convex.

8. In a turbine as defined in claim 2 wherein that portion of saidconvergent portion of the discharge passage upstream of and immediatelyadjacent line contact is concave whereas that portion thereof downstreamof and leading to said constriction is convex.

9. In a turbine as defined in claim 3 wherein that portion of saidconvergent portion of the discharge passage upstream of and immediatelyadjacent line contact is concave whereas that portion thereof downstreamof and leading to said constriction is convex.

1. A turbine for a compressible medium having at least a first stagewheel which is traversed in the centripetal direction by the drivingmedium and operates in accordance with the equal pressure principle,said stage being at least partially surrounded by a distribution duct ofdecreasing cross section, a regulating valve controlling flow into saiddistribution duct and at which an enthalpy difference of the medium isconverted into velocity, said valve comprising a housing provided with avalve body and having a passage which first converges and then divergesand characterised in that in the direction of flow the passage of thevalve housing first converges abruptly and then gradually diverges andin that the valve body leaves free, in the closed state, a narrow gap atthe area of the smallest section of the housing and extends into thediverging part of the housing by a portion whose sectional areagradually decreases in accordance with a linear function of the place ofsaid section on the longitudinal axis of the valve body and in that inthe closed state the valve body is in contact on the upstream side ofthe converging part with the housing along a common tangential planewhich is at an angle to the direction of movement of the valve body,which angle exceeds the friction angle between the valve body and thehousing.
 2. In a turbine driven by a compressible fluid and including atleast one turbine wheel having radial vanes, a housing surrounding saidturbine wheel and defining at least one distribution duct having aninlet end and extending from said inlet end circumferentially of saidturbine wheel in progressively decreasing cross section, the improvementwhich comprises a body portion defining a valve-controlled dischargepassage which discharges the compressible fluid axially into said inletend of the distribution duct; said discharge passage being defined bythe inner surface of said body portion and having a constriction spacedfrom said inlet end of the distribution duct, a divergent portionleading from said constriction to said inlet opening, and a convergentportion leading to said constriction; a valve member concentricallydisposed and axially movable within said discharge passage, said valvemember including a head having a shoulder portion presenting adownstream face engagable with essentially only line contact with saidconvergent portion of the discharge passage upstream of saidconstrictIon when the valve is closed, and a rounded, generally conicalnose having its base merging with said downstream face and presentingthroughout a cross section smaller than that of said constriction, saidconvergent portion of the discharge passage leading abruptly into saidconstriction to provide an annular clearance area around said shoulderportion of the valve member, when same is closed, which is substantiallylarger than the annular clearance between said nose and saidconstriction whereby the angle of engagement between said valve memberand said body portion along said line contact is greater than thefriction angle between such members and wherein the clearance betweenthe nose and the constriction establishes flow control substantially assoon as said line contact between said downstream face of the valvemember and said convergent portion of the discharge passage is broken;and means for axially shifting said valve member between said closedposition and a fully open position in which the tip of said nose of thevalve member remains within said constriction.
 3. In a turbine asdefined in claim 2 wherein said nose is contoured to establish asubstantially linear relation between axial shifting of said valvemember and the change of cross sectional clearance area between the noseand constriction effected by such shifting throughout the range ofmovement of said valve member.
 4. In a turbine as defined in claim 3wherein said downstream face of the valve member is concave.
 5. In aturbine as defined in claim 4 wherein that portion of said convergentportion of the discharge passage upstream of and immediately adjacentline contact is concave whereas that portion thereof downstream of andleading to said constriction is convex.
 6. In a turbine as defined inclaim 2 wherein said downstream face of the valve member is concave. 7.In a turbine as defined in claim 6 wherein that portion of saidconvergent portion of the discharge passage upstream of and immediatelyadjacent line contact is concave whereas that portion thereof downstreamof and leading to said constriction is convex.
 8. In a turbine asdefined in claim 2 wherein that portion of said convergent portion ofthe discharge passage upstream of and immediately adjacent line contactis concave whereas that portion thereof downstream of and leading tosaid constriction is convex.
 9. In a turbine as defined in claim 3wherein that portion of said convergent portion of the discharge passageupstream of and immediately adjacent line contact is concave whereasthat portion thereof downstream of and leading to said constriction isconvex.